Yes, there is a different line for Canadians, and (not sure about this one) for other non-U.S. citizens. You will need to present your passport at check in. Other than that, especially if you have completed online check in, and have your payment form printed and signed, the process is quite painless.
Now--and this is the exception--if you have a concierge cabin, concierge trumps nationality in this case. You just let the people checking health questionnaires that you are in concierge and they will point out the concierge line for you.
Reading along--for debarkation, you just fill out the U.S. Customs form (delivered to your cabin and/or available at Guest Services on the last day of your cruise), and just after you leave the ship, you go to the line for non-U.S. citizens and have your passports and Customs forms available. Sometimes there is a line up, sometimes not. You need to keep your Customs form and passports available to give to the U.S. Customs/Immigration people as you exit the terminal building, after you have collected your luggage.
FYI, we find it simplest to hire one of the luggage porters in the terminal building, and tip generously. The porter will help you collect your luggage, put it on a dolly, take your Customs form(s) and go with you through the line and out of the building. The porter will even assist you in putting your luggage onto a bus or a cab. Well worth a good tip, IMO!